Automatic injection device

ABSTRACT

The invention relates to an automatic injection device comprising a discharge mechanism, a cartridge holder and a cartridge which is slidably accommodated in the holder, the cartridge comprising a glass ampoule having an injection needle connected thereto. A sheath of shrinkable plastic sheet is shrunk around the ampoule entirely or for the greater part thereof.

The present invention relates to an automatic injection devicecomprising an assembly of a discharge mechanism, a cartridge holder anda cartridge which is slidably accomodated in the cartridge holder; thedischarge mechanism comprising a sleeve which is open on one side, aplunger which is movable in the sleeve, a coil spring which acts on saidplunger and tries to move same out of the open end of the sleeveoutwards, a locking device which cooperates with said plunger so as toprevent undesired movement of the plunger, and, if desired, a safetydevice to block said locking device; the cartridge comprising a glassampoule having an injection needle connected thereto, of which ampoulethe part remote from the needle has the shape of a hollow cylinderhaving an entirely or substantially uniform inside diameter, in which ispresent a piston which can be moved by the plunger, and which ampouleincludes an injection liquid or various injection liquids separated fromeach other by stoppers.

Such an injection device, namely for one injection liquid, is disclosedin British Patent Specification No. 1,528,735 in the name of applicants.The device described in said patent specification moreover comprises aspacer element between the plunger and the piston with which the contentof the ampoule can be reduced at will, and a needle guard of a flexiblematerial which keeps the needle sterile during storage of the syringe.Such a needle guard is an excellent provision and is preferably alsoused in the syringe according to the present invention.

Because it is usually not advisable to leave the injection liquid or, ifthe ampoule includes more different injection liquids, the injectionliquid in the front compartment, in contact with the metal of the needleduring the storage time of the syringe, the injection liquid ispreferably separated from the needle by a membrane or stopper. In thatcase, when using the syringe, the access to needle is released when themembrane bursts due to the pressure in the ampoule or when a passage forthe injection liquid is formed through or along the stopper or stoppers.

It has been found that when the device known from said British PatentSpecification No. 1,528,735 is used, fracture of the glass ampoule oftenoccurs. This can be checked by manufacturing the ampoule from glassspecially hardened for this purpose. However, it is particularlydifficult to harden the glass in such manner that a sufficient impactstrength is reached. Therefore, glass ampoules having a sufficientimpact strength are very expensive components for automatic injectiondevices. The force which during use of the device acts on various partsof the device, for example the ampoule, must be large because theinjection needle has first to be forced into the user's body, oftenthrough the clothes, and the injection liquid has then to be injected.In order to be able to meet these requirements, a powerful coil springmust be used having a spring-power of at least approximately 120 N. Inthis case, however, there is a fair chance that when using the syringethe material of the ampoule cannot withstand the forces occuring uponrelaxation of the spring, as a result of which fracture of the glassampoule frequently occurs when unhardened glass is used.

In the case of fracture of the glass ampoule, the injection liquidusually leaks away out of the ampoule before it can be injected, so thatthe automatic injector fails at the critical instant.

It is the object of the present invention to provide an automaticinjection device which does not exhibit the above-mentioneddisadvantage.

This object can be achieved by means of an automatic injection device ofthe kind described in the opening paragraph which comprises a sheath ofa shrinkable plastic sheet which is shrunk around the ampoule so thatthe ampoule in the longitudinal direction entirely or for the greaterpart is covered by the sheath of shrinkable sheet. Such a sheath forenveloping a part of the ampoule of a disposable syringe, albeit with adifferent purpose, is known from the non-pre-published NetherlandsPatent Application No. 8103476 in the name of Applicants. The sheath ismanufactured from a known plastic sheet which as a result of heating canshrink in at least one (axial) direction, for example, a prestretchedsheet of PVC.

It has surprisingly been found that when such a sheath of shrinkablesheet is used, the possibility of fracture of the ampoule is reduced insuch manner that an ampoule of unhardened glass may be used without anyobjection. This was not to be expected at all, because the wallthickness of the ampoule hardly increases as a result of the use of asheath of shrinkable sheet: the glass wall of an ampoule commonly usedfor automatic injection devices is approximately 0.9 mm thick (tolerance0.06 mm); the wall thickness of the shrunk sheet is approximately 0.06mm.

During the assembly process of the injector, the sheath of shrinkablesheet can very simply be slid around the ampoule and be shrunk aroundthe ampoule as described in the above-mentioned Netherlands PatentApplication No. 8103476.

According to another aspect of the present invention, the risk offracture of the glass ampoule can be even further reduced by providingthe syringe with an annular member of a slightly resilient materialwhich is provided on the open end of the ampoule remote from the needle.Such a provision can also be used very simply and hence cheaply. Theannular member, preferably of a synthetic resin, for example,polypropylene, can simply be provided on the rear edge of the openampoule during assembly of the syringe, after which the sheath ofshrinkable sheet is preferably shrunk around both the ampoule and theannular member. The annular member may also be used alone, hence withoutthe sheath of shrinkable sheet, namely between the sleeve of the firingmechanism comprising the spring and the plunger, and the end of theampoule remote from the needle. A considerable improvement is alsoachieved in this case, preferably, however, the annular member is usedtogether with the sheath of shrinkable sheet, because as a result ofthis combination the possibility of fracture of ampoules manufacturedfrom unhardened glass can be minimized.

In order to prevent movement of the annular member during assembly orduring storage of the syringe, the annular member is preferablyconstructed so as to have approximately the same outside diameter as theampoule, a slightly smaller inside diameter than the end of the ampouleremote from the needle, and a neck fitting within said end of theampoule.

Alternatively, the above sheath of shrinkable sheet may be shrunk notonly around the ampoule body but also inwardly around the rear edge ofthe ampoule, thus covering said rear edge completely. This provision hasproved to substantially prevent fracture of the glass ampoules, even inthe absence of the above annular member, and thus forms a preferredprovision in view of the cost-price of the device.

The injector described in the above-mentioned British PatentSpecification No. 1,528,735 comprises a plunger which consists of a headfacing the piston and forming on the rear side of an abutment for thecoil spring, a central part having a uniform circumference around whichthe coil spring fits, and a furcated end part of reduced circumferenceremote from the piston and the resilient prongs or detent arms of whichcooperate with the locking device. According to still another aspect ofthe present invention, the risk of fracture of the glass ampoule whenusing an automatic injection device comprising such a plunger can beeven further reduced by providing around the end part of the plunger asleeve which is open at each end and has an outside diameter which isapproximately equal to that of the central part of the plunger. Thesleeve is manufactured from form-retaining material, for example, asuitable synthetic resin or, preferably, metal. The above-mentionedprongs of the plunger must be sufficiently resilient to enable both theassembly in the locking device and the activation of the syringe.Therefore, the prongs are comparatively narrow so that the end part ofthe plunger has a smaller circumference than the central part. It hasnow been found that by providing a sleeve around said end part, thepossiblity of fracture of the ampoule is further reduced. Such a sleevemay be used together with one of the two or with both above-mentionedprovisions in order to reach the desired improvement of the automaticinjector.

The above-mentioned provisions to reduce the possibility of fracture ofthe glass ampoule of an automatic injector are meant in particular foran automatic injection device whose ampoule is manufactured fromunhardened glass. When the glass has been subjected to a specialhardening, the possibility of fracture is comparatively small. However,such a hardening method, as already stated hereinbefore, is particularlycomplicated and hence very expensive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in greater detail withreference to a preferred embodiment which is shown in the drawing, inwhich;

FIG. 1 is a longitudinal sectional view of a injector according to theinvention;

FIG. 2 is a longitudinal sectional view of a cartridge having an ampouleon the open end of which the annular member has been provided;

FIG. 3 shows the same cartridge, this time provided with an annularmember and a sheath of shrinkable sheet; and

FIG. 4 shows the rear end of the ampoule, provided with a sheath ofshrinkable sheet only.

In broad outline, the device shown in FIG. 1 does not differ from thatdescribed and shown in the British Patent Specification No. 1,528,735mentioned before.

The embodiment shown in FIG. 1 is only one embodiment of an automaticinjection device in which the provisions to reduce the possibility offracture of the glass ampoule can advantageously be used. Other suitableexamples of injectors are described and shown in non-pre-publishedNetherlands Patent Application No. 8103744 in the name of Applicants.

The injector shown in FIG. 1 comprises an outer sleeve 1 having inwardlybent edge 2 and circumferential groove 3 in which a cartridge assembly 4and a discharge mechanism 5 are accomodated. The cartridge assemblycomprises a cartridge holder 6 which fits in the outer sleeve and on itsfront end has a circular aperture 7, and a cartridge 8 which is movablein the cartridge holder. The cartridge comprises an ampoule 9 withinjection liquid 10, a piston 11 at one end and a needle 13 having aneedle guard 12 at the other end, said needle being connected to theampoule by means of a needle holder 14. A membrane 15 is providedbetween the neck of the ampoule and the needle holder and, duringstorage of the syringe, keeps the injection liquid separated from theneedle but, during use of the syringe, bursts open so that the injectionliquid can reach the needle cannula. Finally, a spacer element 16 isprovided behind the piston with which the volume of the ampoule for theinjection liquid has been reduced.

As in the injector described in British Patent Specification No.1,528,735, the discharge mechanism comprises an outer gun sleeve 17locked (at 3) in the outer sleeve 1, an inner gun sleeve 18 slidablyaccomodated in the outer gun sleeve and comprising a coil spring 19. Thecoil spring fits around a plunger 20 with a sufficient amount of play,the plunger consisting of a plunger head 21 which is inserted in thespacer element, a central part 22 having a uniform circumference, and anend part 23 of reduced circumference. The end part consists of fourresilient prongs or detent arms the conical ends 24 of which bear on ametal sealing ring 25 around an aperture in the rear face of the innergun sleeve. In the syringe shown in FIG. 1, the safety member consistingof a cap having a safety pin which may extend between the prongs of theplunger, has already been removed so that the syringe is ready for use.

A sheath 26 of PVC shrinkable sheet is shrunk around the whole ampoule,including the neck.

An annular member 27 of polypropylene is provided on the rear edge ofthe ampoule. This is shown more clearly in FIG. 2 in which the cartridgewith the ampoule 9 and the annular member 27 are illustrated on aslightly larger scale. The annular member comprises a neck 28 which fitswithin the rear edge of the ampoule.

FIG. 3 shows the same cartridge, this time provided with annular member27 and sheath of shrinkable sheet 26. The latter is shrunk around theampoule 9, a part of the needle holder 14 and the annular member 27. Asa result of this the annular member remains located during assembly ofthe injector. Furthermore, around the resilient prongs of the plunger(FIG. 1) is present a metal sleeve 29 which is open at each end and theoutside diameter of which is approximately equal to the diameter of thecentral part 22 of the plunger.

In the embodiment of FIG. 4, showing the rear end of the ampoule, theannular member is not present. The sheath of shrinkable sheet 26completely envelopes the rear edge of the ampoule 9.

It will be obvious that it is not necessary for all provisions to bepresent collectively, as is shown in the FIG. 1 embodiment. The sheathof shrinkable sheet may also be used advantageously alone (FIG. 4), ortogether with the annular member (FIG. 3), or together with the sleeve;and the annular member may be used alone (FIG. 2) or together with thesleeve. These embodiments are clear without further explanationtherefore not all of them have been illustrated by means of Figures.

The use of the injector according to the present invention is the sameas that of the one described in the above-mentioned British PatentSpecification No. 1,528,735 and need no further explanation.

Injectors according to the present invention in which the ampoule hadbeen manufactured from unhardened glass, were compared in theirapplication with identical injectors without the provisions describedand with the same injectors having ampoules of hardened glass. Thefollowing results were obtained.

    ______________________________________                                               Injector Number of   Well emptied                                      Provision                                                                              glass ampoule                                                                            tested inj. number %                                      ______________________________________                                        sheath of                                                                              unhardened 200         198    99.0                                   shrinkable                                                                    sheet                                                                         Annular  unhardened 200         187    93.5                                   member                                                                        sheath plus                                                                            unhardened 200         200    100                                    annular                                                                       member                                                                        None     unhardened 200         169    84.5                                   None     hardened   300         298    99.3                                   ______________________________________                                    

"Well emptied" is to be understood to mean herein that during use of theinjector the syringe liquid has left the injector through the injectionneedle and has not leaked away prematurely as a result of fracture ofthe ampoule. In the comparative experiments reported on in the abovetable, the sheath of shrinkable sheet was not shrunk around the rearedge of the ampoule. When the sheath was also completely shrunk aroundthe rear edge of the ampoule (as in FIG. 4), of the 50 glass ampoulestested, a number of 50 (100%) was well emptied. From the above resultsit is apparent that the percentage of fractured ampoules of unhardenedglass can be reduced considerably by means of the provisions asindicated, and that by a correct choice of the provisions at least anequally great reliability can be achieved as in identical injectorshaving ampoules of hardened glass.

Although the preceding disclosure illustrating the ampoule as containingonly one injection liquid, the ampoule may contain various injectionliquids separated from each other by stoppers.

We claim:
 1. An automatic injection device, comprising an assembly of adischarge mechanism, a cartridge holder and a cartridge slidablyaccommodated in the cartridge holder; the discharge mechanism comprisinga sleeve that is open on one side, a plunger that is movable in thesleeve, a coil spring that acts on said plunger to move same toward theopen end of the sleeve, a locking device that cooperates with saidplunger to prevent undesired movement of the plunger; the cartridgecomprising a glass ampoule having a needle connected to one end thereofand being open-ended at the opposite end thereof, a part of said ampouleremote from the needle comprising a hollow cylinder having an entirelyor substantially uniform inside diameter, a piston adapted for movementby the plunger being provided in said cylinder, a movable inner sleevesurrounding said coil spring and adapted to bear against said ampoule atits open end; said syringe being characterized in that the ampoulecontains at least one injection liquid; said syringe being furthercharacterized in that an annular member of slightly resilient materialis interposed between the open end of the ampoule remote from the needleand said movable inner sleeve.
 2. An injection device as claimed inclaim 1, wherein the annular member has approximately the same outsidediameter as the ampoule, has a slightly smaller inside diameter than theend of the ampoule remote from the needle, and includes a neck portionthat fits within the end of the ampoule remote from the needle.
 3. Aninjection device as claimed in claim 1, wherein the plunger comprises ahead facing the piston and forming on the rear side an abutment for thecoil spring; a central part of uniform circumference around which thespiral spring fits; and a furcated end part of reduced circumferenceremote from the piston, said syringe being characterized in that asleeve that is open at each end is provided around the end part, theoutside diameter of said sleeve being approximately equal to that of thecentral part of the plunger.
 4. An injection device as claimed in claim2, wherein the plunger comprises a head facing the piston and forming onthe rear side an abutment for the coil spring; a central part of uniformcircumference around which the spiral spring fits; and a furcated endpart of reduced circumference remote from the piston, said syringe beingcharacterized in that a sleeve that is open at each end is providedaround the end part, the outside diameter of said sleeve beingapproximately equal to that of the central part of the plunger.
 5. Aninjection device as claimed in claim 1, characterized in that saidampoule contains various injection liquids separated from each other byat least one stopper.
 6. An injection device as claimed in claim 1, saidsyringe being further characterized in that a sheath of plastic sheet isshrunk around said annular member and said ampoule entirely or for thegreater part thereof.